Hi For NTP levels of accuracy Glonas is quite fine. Combining that with GPS should get you a pretty good “time source” even under your extreme conditions.
Bob > On Oct 31, 2017, at 11:14 PM, MLewis <[email protected]> wrote: > > I'm stuck with a near ground level antenna site (~16" above grade?), with > half a sky view (thankfully to the SSE), less some low blocking buildings > with regular mutlipath, plus multipath bouncing off a taller building to the > SE that bounces sats from the NW at me from low over the Bering Strait. The > building I'm in is concrete with flat steel under each floor from the > construction method. As I write this I'm down to two green sats in LH. > > A number of times a day, it will drop to one sat, and there's a few dropouts > a day where it goes to none of sufficient signal. How many times and for how > long varies by the day. It's worse when it's wet out, which it is right now. > If I lower the signal strength threshold, then I end up with tons of > multipath signals. > > If I can ever get a bios update to my NEO-M8T, then I'll have GAL in the mix > and should experience fewer dropouts, potentially none. > > An RTC that +/- 3 PPM over 24 hours would be great for holdovers of one to 20 > minutes. > > While I wrote this, LH was typically showing two or three green sats, once up > to five and once down to one. And I just hit a dropout... for a minute and a > half; the one remaining green sat went behind the corner of the building's > entrance canopy, then back out. > > > On 31/10/2017 10:30 PM, Bob kb8tq wrote: >> Hi >> >> Under what conditions would you expect to loose GPS? I seem to be able to >> do just fine sitting in an armchair here in the family room. That’s hardly a >> fancy setup. >> >> Bob >> >>> On Oct 31, 2017, at 10:27 PM, MLewis <[email protected]> wrote: >>> >>> I'm intending to add a "precision" (well, precision to the Pi world) RTC to >>> my Pi 3 to use for a holdover source when it hasn't got PPS from the GPS >>> module. >>> >>> On 31/10/2017 10:04 PM, Chris Caudle wrote: >>>> On Tue, October 31, 2017 7:19 pm, MLewis wrote: >>>>> ...the "better" quality RTCs seem to be DS3231 based >>>>> How does one translate that into an expected 24 hour holdover? >>>> For the RTC, or for an NTP server? If the NTP server is running it will >>>> not make a difference, modern operating systems do not use the RTC for the >>>> system clock, only to get close to the correct time at startup. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
